The concept of treating water with of metallic ions to kill bacteria in a body of water is known in the art. A metallic ion such as a silver ion is an effective bactericide for a body of water including recreational water such as swimming pools, spas, jetted tubs or the like and is a preferred material because it is generally easier and safer to use than other known bactericides or algaecides. A further advantage of using silver ion as a bactericide is that silver ion minimizes the need for pH adjustment of the body of water. However, if the concentration of metallic ions such as silver ions in a body of water is too low the ability to kill microorganisms is reduced or lost. On the other hand if the concentration of metallic ions such as silver ions is too high it can be harmful to those who use the body of water. Thus when silver ion is used as a disinfectant in a body of water one generally want to maintain the concentration of the silver ion in an effective range to kill microorganisms.
The concept of introducing biocidal metals into a body of water to generate biocidal metal ions, such as silver ions, to sanitize the body of water is known in the art. The use of these ions to purify the body of water results in decreased need for chlorination. An example of a method of introducing biocidal metal ions into water involves the use of sacrificial electrodes containing metals corresponding to the desired ions, including alloys of silver and copper, and electrolytically dissolving the metals into the water. Other methods of introducing biocidal metal ions into water include contacting the water with substrates that have been coated or impregnated with pure or alloyed metal, soluble metal salts, or some combination thereof.
Traditionally, the sources of metallic ions used to kill bacteria in recreational water have been limited to metallic ion donors that are readily soluble in the recreational water in order to maintain an effective concentration of the biocides in the body of water. Silver chloride (AgCl), for example, has been a commonly used bactericide for releasing silver ions into the body of water to effectively kill microorganisms. Sodium bromide has also been known to be used with silver chloride to provide an additional and alternative water disinfection system.
One of the problems associated with the use of silver for killing microorganisms is that silver has a tendency to complex with other compounds and become increasingly insoluble thereby reducing the effective microorganisms killing ability of the silver. For example, it would not be anticipated that silver chloride when used in combination with sodium bromide would be an effective disinfectant system because of the combination's tendency to form insoluble bromide crystals, which are not believed to be biologically active in aqueous environments. However, it has been discovered that if silver forms a complex with hydantoins, the silver will remain soluble to a higher degree thereby retaining the silver's antimicrobial activity.
The present invention includes a device and method for using metal ion donors in combination with hydantoins including unhalogenated hydantoins such as 5,5-dimethylhydantoin (hereinafter “DMH”) to enhance a concentration of the metal ions in the body of water or to enhance the solubility of metal ions from other metal ion donors to retain the silver's antimicrobial activity in the water.